GFP and jelly fish

The GFP gets the excitation light from aequorin luminescence. Aequorin
luminescence is induced by an elevation of calcium concentration.
Calcium is elevated in response to stress. The theory is that the light
produced scares predators.
Gidi.
Himadri K Samanta wrote:
> I was wondering how the green fluorescent protein works in jelly
> fish. If it glows at night, how does GFP gets the light for
> excitation? What is the usefulness of it to the jellyfish? Does
> other organism also carry similar protein? Thanks.